ABSTRACT
Besides the merits of energy saving, form factor, long lifetime, and durability, light-emitting diodes (LEDs) also provide a much higher degree of freedom to tune the light emission spectrum compared to conventional lighting technologies. The freedom not only provides new opportunities to optimize these LED-based light sources but also introduces challenges to characterize the spectrum. Several studies have indicated that the existing international measures (and standards), which are currently widely adopted in the lighting industry for conventional lighting, are outdated, improper, or at least insufficient to specify the multidimensional light-quality properties of LED-based white light sources. The LED technology also allows for tailored solutions for different applications that require a more sophisticated description of the light-quality properties during the design and development process. Furthermore, dynamics of LED spectrum magnify the urgency of proper assessment and evaluation of light quality for LED lighting. However, this turns out to be a big challenge for the researchers and experts of color science and industrial specifiers. On the other hand, it does also bring an opportunity to reexamine the limits of existing methods and approaches and thus develop and propose more meaningful measures to describe the performance, with regard to applications in performing specific visual or even nonvisual tasks. In this chapter, we outline some key aspects of the quality of light, which are determined by the emission spectrum of white-light source. Relevant characterization methods are introduced and reviewed, and their boundaries are explored. The latest developments are also discussed.
